This invention relates to electronic keyboards in general and, more specifically, to keyboards with double entry protection and parallel encoding.
Conventional keyboard systems include momentary contact keys which may be represented schematically as matrices having rows and columns, each key of which is sequentially scanned at a rate determined by an internal clock. These systems have here-to-fore required relatively complex circuitry to facilitate parallel entry of data. Furthermore, the possibility of errors in the system is fairly high. For example, depressing a pair of keys simultaneously usually results in error entry. Other errors are introduced by key bounce, which is the mechanical vibratory action of the contact making and breaking, and ghosting effects when three adjacent keys forming a partial square on the matrix are pressed.